These were the largest minesweepers ever built
for the Royal Navy, and were frequently used as escort vessels
during World War II.
The reason was that they were designed to combat every single
type of mie around, and had to ship LL sweeps, acoustic hammers
as well as conventional style sweeping gear. Thus, they were 40'
longer and 7' beamier than the previous Bangor class,
and the design was so suddesful, it continued right through the
war until the cessation.
So there would be no hold ups in supply, a design with
recoprocating and one with turbine machinery was prepared, and of
53 to be built in the UK, 31 had reciprocating and 21 had
turbines. The USN too was deficient in minesweepers when the war
started, and put this design in hand, and even transferred 15 (
built for them in Canada ) to the RN. 12 more RCN vessels were
tranferred, for 4 "Flower" and 12 "Castle"
corvettes.
Due to supply problems, early vessels shipped 4 single instead of
twin 20mm cannon, and from 1944, 4 40mm Bofors were shipped
instead. SW type 271 was carried on the bridge, and AW type 291
on the foremast. The large sweep deck was sufficientyl big to
carry four DC lobbers and a 2 DC racks.
Of the original 100 ships ordered, 6 were cancelled and 6 were
war losses. Postwar many were transferred or sold to Commonwealth
or foreign navies, or assigned to RNVR units.
The ships were built in British and Canadian yards; construction
time varied, but Wave was built in the incredible time
of 3 days short of 8 months.